Question 522518
Identify the conic section:
{{{x^2+y^2-4y-5 = 0}}} Add 5 to both sides.
{{{x^2+(y^2-4y) = 5}}} Complete the square in y by adding 4 to both sides.
{{{x^2+(y^2-4y+4) = 5+4}}} Factor the group in y and simplify.
{{{x^2+(y-2)^2 = 9}}} Compare this with the standard form for a circle of radius r with center at (h, k).
{{{(x-h)^2+(y-k)^2 = r^2}}} and you can see that you have a circle of radius 3 with center at (0,2).
I forgot the graph:
{{{graph(400,400,-5,5,-5,6,sqrt(-x^2+9)+2,-sqrt(-x^2+9)+2)}}}